1. Field of the Invention
The present invention relates to the field of electrical pin-and-socket type connectors that are intended for use in volatile, conductive or corrosive environments. Connectors of this sort generally have receptacles with socket contacts that are sealed from the exterior environment before, during and after mating and demating. There is one category of these that accomplish the sealing by having the connector receptacle filled with dielectric fluid that is retained by penetrable seals within the receptacle. The fluid is free to move about within the receptacle, and thus is displaced as the plug pins enter during mating. One or more flexible elements are generally provided to accommodate the increase in volume within the receptacle due to the insertion of the plug pins.
2. Description of the Related Art
Typical examples of related art are given in U.S. Pat. Nos. 5,203,805, and 4,948,377 which are suggested as reference material. For clarity in the following discussion the term "module" refers to the assembly that makes-up each individual circuit within the connector, whereas the term "common" refers to features which are shared by all circuits. For instance, the outer shell of such a connector would be a "common" feature, whereas an individual electrical socket would be a feature of one of the circuit "modules" within the connector. In these examples each socket of the receptacle portion of the connectors is constructed as a separate module housed within a respective separate, sealed, flexible-walled chamber. Within the chamber is a spring and an elongated-shaft stopper. The stopper is urged outward (toward the receptacle mating face) by the spring, but is captured in such a way as to limit its outward travel to a point where the tip of its elongated shaft just reaches the mating face of the receptacle. The chamber has an elastic end-seal which constrictively fits to the shaft of the stopper and thus seals to it. All other interfaces of the chamber are affixed with seals so that the chamber may be filled with dielectric fluid and does not leak.
The corresponding connector plug which mates to the above described connector receptacle has respective plug pins that mate to their respective receptacle sockets. Each such plug pin has an elongated shaft sheathed in a dielectric covering, and has an exposed conductive tip. The pin has substantially the same diameter as the stopper of its respective receptacle socket, although the pin is often just slightly larger in diameter for reasons not important here, but discussed later.
When the above described plug and receptacle are mated, the tip of each respective plug pin engages the tip of each respective stopper and forces it inward into its socket, meanwhile compressing the spring. The fluid which is displaced by the entrance of the pin into the fluid-filled receptacle is accommodated by a compliant element of the module chamber which flexes, increasing the chamber's volume.
Demating the connector results in the reverse sequence of events. As each pin is withdrawn from its socket, the spring causes the socket's stopper to faithfully follow the pin outward into the end seal of the module chamber. The end seal is therefore always occupied, either by the plug pin or by the stopper, and does not leak dielectric fluid out or allow the material of the outside environment (eg. seawater) to seep in.
It will be appreciated in contemplating the foregoing sequence of actions that the socket's electrical contacts, being well within the module's fluid chamber, never are exposed to, or have contact with the outside environment. Therefore, the socket contacts can remain electrically energized before during and after mating and demating the connector. And any arcing which may occur during these actions is contained within the dielectric fluid, so that such connectors are spark-proof to the outside environment.
As may be seen in the referenced examples, to gain an additional measure of isolation of the socket electrical contacts, the above described socket modules are separated from the outside environment by an additional fluid volume and one or more additional end-seals through which the stopper sealably passes in the unmated condition, and through which the plug pin sealably passes in the mated condition. Thus when mated, each respective plug pin engages the tip of each respective stopper and urges it inward through a first end-seal, through an intermediate fluid bath, and then through an additional constrictive seal, and into the socket module's fluid-filled chamber. When fully mated, therefore, the conductive tip of the plug and the electrical contact of the socket are fully contained in dielectric fluid within the socket-module chamber and are separated from the exterior environment by two seals which themselves are separated by an additional dielectric fluid bath or chamber.
The additional fluid chamber and seal offer several advantages: The additional chamber (bath) provides a depository for contaminants that might slip past the first seal, and the second seal acts as an additional wiper as well as prohibiting the free migration of contaminants from the added bath into the inner module chamber containing the electrical contacts.
The above references demonstrate two methods used to provide the additional bath and seal. The U.S. Pat. No. 4,948,377 patent shows all of the previously described socket modules housed within a larger "common" chamber. The common chamber has a multiplicity of ports through its elastomeric end wall that constrictively seal to the elongated shafts of the stoppers in the unmated condition, and to the plug pins in the mated condition. As mating of the '377 connector proceeds, the respective plug pins engage the tips of their respective stoppers and urge them inward. Each plug pin passes through a first seal, which is an elastomeric port in the end-wall of the common chamber, thence through the common oil chamber, in which any contaminants that slip past the first seal are expected to be deposited, and thence through a second seal and into the individual module oil-chamber of its respective socket module. The arrangement offers an improvement over earlier related art such as described in U.S. Pat. Nos. 4,142,770 and 3,729,699 which had only single seals and baths. But it still has a disadvantage that any contamination which might enter into the common bath (chamber) from any one of the end ports, as might occur if the elastomeric port were damaged, would contaminate the whole common bath surrounding all of the socket modules. A flaw in any one of the common-chamber elastomeric ports could therefore negate the beneficial effect of the outer bath for all of the module chambers. As a point to be returned to later, it will be noted that in the '377 embodiment the socket modules are completely contained within the outer common chamber; therefore, as the modules swell and retract due to the insertion and withdrawal of the plug pins so must the common chamber flex to accommodate the changing volume.
The possibility of contamination of the common chamber via a single failed end-seal, as well as other improvements, are addressed in the art of U.S. Pat. No. 5,203,805. In that patent, an embodiment is described that creates a separate, second, outer (in the sense of being toward the mating-face of the receptacle) chamber and end-seal for each socket module, said elements being axially aligned with the inner socket-module chamber, stopper and end-seal. And although there is still a common all-surrounding chamber, it is a sealed chamber with no communication to any other volume. It therefore is not subject to contamination. The axially aligned second bath and end seal are a part of each module, and do not communicate with the common chamber or with the chambers of any of the other modules in the connector. In that embodiment, there is free communication between the module's inner fluid-filled chamber and second, outer chamber (bath) of each socket module in the unmated condition. The communication is allowed via flow past a narrowed segment of the stopper.
The communication of fluid between the two axially-aligned module chambers of the '805 socket module is cut-off in the mated condition by the engagement of the interior seal with the plug-pin shaft. But in the unmated condition limited communication is permitted by flow past the small-diameter segment of the stopper. That allows replenishment of any fluid lost from the module's outer chamber with fluid from the module's internal chamber when the connector is unmated, but still serves to substantially retain contaminants within the outer chamber. The design of the '805 patent is very successful, but still has some drawbacks. One drawback is that the narrowed stopper is not as robust as would be desired. A second is that the end structure of the socket module which is comprised of the outermost seal, the outer chamber wall, and the narrowed stopper is not well supported, and is flimsy. In use, the whole end of the module assembly could be pushed inward, out of position in the overall connector assembly, and damage to the narrowed stopper can occur. The thin outer-chamber wall is likewise subject to easy damage. These drawbacks, coupled with a desire to provide multiple more than two wipers within the end-seal complex has prompted the improvements which are the subjects of the present patent application.
These improvements are made possible in part by the realization that the outer chamber of the '805 socket module need not be volume (or pressure) compensated. The '805 outer module chamber has a thin, flexible outer wall intended to flex in and out to accommodate volume changes within it due to the sliding passage of the pin and stopper through it during mating and demating. But this outer module chamber communicates to the inner chamber at all times except when the plug pin is inserted through it. During the mating sequence the plug pin passes through the end seal and into the outer module chamber. Fluid in the outer module chamber that is displaced by the plug is free to flow into the inner module chamber up until the point where the entering plug pin seals-off the passage between the outer and inner chambers. But at that point, even though the shaft of the pin continues to slide through the outer module chamber, no net additional material enters the outer module chamber. As a new portion of the plug-pin shaft slides in one end, an old portion slides out the other end. Once sealed-off by the entering pin, at which point it actually becomes a separate chamber, the volume of the outer module chamber is constant. The same argument is applicable when the pin is withdrawn during demating. So no volume compensation of this outer module chamber is necessary to accommodate the insertion/withdrawal of the plug-pin during mating/demating. One might argue that some small-scale volume compensation in the outer module chamber might still be necessary to account for material bulk-property changes that might occur to the oil and the elastomeric outer-chamber body as a result of thermal or pressure effects. But these are easily overcome by choosing elastomers and dielectric fluids that have identical thermal expansion and pressure contraction coefficients. In fact the silicone oil and rubber compounds used in these connectors do have identical thermal and pressure coefficients. It is well known that in reaction to applied pressure, elastomers behave as fluids for small displacements, so the dielectric fluid and the outer chamber walls react in harmony to pressure and thermal effects. It is as if they were a single substance. So in fact, no volume compensation is required of the outer module chamber.
Another point alluded to earlier is the additional realization that the '805 outer socket-module chamber, being axially aligned with the inner socket-module chamber, need not react to volume changes of said inner chamber. In the '377 connector, the inner socket module is completely enclosed by the outer common chamber, which common chamber also served as the outer chamber to the socket-module. Thus, in the '377 connector the outer chamber had to expand to accommodate the insertion of the plug pin because the insertion caused the module chamber to expand, and the module chamber was completely within the outer chamber. In the '805 connector the common chamber does likewise have to expand, but that has nothing to do with the outer module chamber.
As will be seen, the present invention takes advantage of these realizations to provide an improved connector having a ruggedized construction and efficient, multiple module end-seals.